<timer>
    <p>Seconds Elapsed: { time }</p>
    <script>
        this.time = ~~(opts.start || 0);
        this.step = ~~(opts.step || 1);
        tick()
        {
            this.update({time: this.time + this.step});
        }
        var timer = setInterval(this.tick, 1000);
        this.on('unmount', function () {
            clearInterval(timer);
        });
    </script>
</timer>